With the rapidly increasing demands for multimedia services, there is a demand for mobile communication systems to provide high-speed data transmissions in a reliable manner. In order to enable high-speed data transmission over a wireless channel, which uses limited bandwidth and power, it is essential to increase capacity. In recent times, there has been a continued increase of interest in technologies for improving capacity.
In a wireless communication environment, the reliability of reception signals may be greatly degraded by fading, shadowing, wave attenuation, interference, etc. Thus, in order to enable high-speed data communication, these wireless channel properties must be overcome, or an alternative is required which utilizes such qualities. A technology proposed in answer to such needs is the MIMO antenna technology.
The MIMO antenna technology uses a spatial multiplexing technique for transmitting data at high speeds without further increasing the system's bandwidth, by using multiple antennas at the transmitter or receiver to transmit different data simultaneously.
A MIMO antenna has an arrayed antenna structure that uses multiple radiators, and since a multiple number of radiators are used, there can be interference occurring between the radiators. Such interference can distort the radiating pattern or create a mutual coupling effect among the radiators.
In order to minimize interference between radiators, a MIMO antenna may use an isolation element, i.e. a separate feature, or may use a structure in which the radiators are widely separated from one another.
With existing isolation methods obtained from prior research, providing the desired isolation basically involves providing a sufficient distance between two antennas, even in cases where a separate isolation element is used.
However, since the demand for smaller terminals is an ongoing requirement, and since providing a sufficient distance between multiple antennas not only is very difficult but also runs contrary to providing smaller terminal sizes, there is a need for an isolation technique that can be applied for multiple antennas that are positioned relatively closely to one another.